Refers to a school or university club focused on mountaineering and hiking.
He joined the mountaineering club in high school.
mountain area; mountainous region
A somewhat formal or literary term for a mountainous area; in everyday speech, 山間部 or 山地 is more common.
Rare plants can be found in that mountainous area.
Also means mountaineering club, but 山岳部 is the more established term in many schools.
Compound of 山岳 (mountain) + 部 (club, section, or area). The derivation is straightforward from the kanji meanings.